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Alexandros Frantzis - One of the best experts on this subject based on the ideXlab platform.
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evidence of introgressive hybridization between stenella coeruleoalba and Delphinus Delphis in the greek seas
Molecular Phylogenetics and Evolution, 2018Co-Authors: Aglaia Antoniou, Paraskevi Alexiadou, Nefeli Paschou, Nikos Poulakakis, Alexandros FrantzisAbstract:Abstract Natural interspecific hybridization might be more important for the evolutionary history and speciation of animals than previously thought, considering several demographic and life history traits as well as habitat disturbance as factors that promote it. In this aspect, cetaceans comprise an interesting case in which the occurrence of sympatric species in mixed associations provides excellent opportunities for interspecific sexual interaction and the potential for hybridization. Here, we present evidence of natural hybridization for two cetacean species commonly occurring in the Greek Seas (Stenella coeruleoalba and Delphinus Delphis), which naturally overlap in the Gulf of Corinth by analyzing highly resolving microsatellite DNA markers and mitochondrial DNA sequences in skin samples from 45 individuals of S. coeruleoalba, 12 D. Delphis and three intermediate morphs. Employing several phylogenetic and population genetic approaches, we found 15 individuals that are potential hybrids including the three intermediate morphs, verifying the occurrence of natural hybridization between species of different genera. Their hybrids are fertile and able to reproduce not only with the other hybrids but also with each of the two-parental species. However, current evidence does not allow firm conclusions whether hybridization might constitute a step towards the generation of a new species and/or the swan song of an already existing species (i.e., D. Delphis). Given that the focal species form mixed pods in several areas of Mediterranean, this study is an excellent opportunity to understand the mechanisms leading to hybridization in the context of gene flow and urges for the evaluation of the genetic status of common dolphins in the Mediterranean.
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linking small pelagic fish and cetacean distribution to model suitable habitat for coastal dolphin species Delphinus Delphis and tursiops truncatus in the greek seas eastern mediterranean
Aquatic Conservation-marine and Freshwater Ecosystems, 2017Co-Authors: Marianna Giannoulaki, Paraskevi Alexiadou, Evangelia Markoglou, Vasilis D Valavanis, Anna Cucknell, Alexandros FrantzisAbstract:A large-scale assessment of the summertime suitable habitat for Delphinus Delphis (short-beaked common dolphin) and Tursiops truncatus (common bottlenose dolphin) in Greek Seas (Eastern Mediterranean) was conducted using data from dedicated and opportunistic cetacean surveys and published data records. Using a presence/absence approach, generalized additive models were applied to define a suite of environmental, bathymetric and biotic factors that best describe common and bottlenose dolphin spatial distribution, during early (May, June, July) and late (August, September) summer. A geographic information system (GIS) was used to integrate sightings data with environmental characteristics, distance from the coast and sardine probability of presence. These variables were considered as good proxies for defining species-suitable habitat within the study area's coastal environment. The final selected models were used to produce annual probability maps of the presence of the species in the entire Greek Seas, as a measure of habitat suitability. Based on the mean probability and standard deviation maps for the study period GIS techniques were subsequently used to determine the persistent (areas with high mean and low variation) and occasional (high mean and high variation) habitat of each species. Results showed that there was a high probability of common dolphin presence in areas with a high probability of sardine presence. For bottlenose dolphin, higher probability of the presence of species occurred in areas closer to the shore, with a high probability of sardine presence and with high concentrations of chlorophyll-a. In both seasons, the North Aegean Sea and the Inner Ionian Sea Archipelago were indicated as the most suitable areas for common dolphin distribution. Persistent habitat areas of the bottlenose dolphin included enclosed seas, continental shelf waters, and waters surrounding islands. The indicated suitable areas are discussed along with deficiencies of the models and future implications for conservation. Copyright © 2016 John Wiley & Sons, Ltd.
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ecology status and conservation of short beaked common dolphins Delphinus Delphis in the mediterranean sea
Mammal Review, 2003Co-Authors: Giovanni Bearzi, Alexandros Frantzis, Ana Canadas, Randall R Reeves, Giuseppe Notarbartolodisciara, Elena Politi, Barbara MussiAbstract:The recent decline in the Mediterranean population of short-beaked common dol- phins Delphinus Delphis has been the subject of scientific controversy and political indifference. Research on these animals has been very limited and there has been no large-scale, systematic effort to assess and monitor their abundance and distribution. The consequent lack of data has prevented a good understanding of historical and ongoing trends. 2. Nonetheless, literature and osteological collections confirm that common dolphins were widespread and abundant in much of the Mediterranean Sea until the late 1960s and that their decline occurred relatively quickly. Today, common dolphins remain relatively abun- dant only in the westernmost portion of the basin (Alboran Sea), with sparse records off Algeria and Tunisia, concentrations around the Maltese islands and in parts of the Aegean Sea, and relict groups in the south-eastern Tyrrhenian and eastern Ionian Seas. Otherwise, these dolphins are rare in, or completely absent from, Mediterranean areas where informa- tion is available. 3. Circumstantial evidence and qualitative judgements by the authors suggest that the fol- lowing factors may have contributed to the decline of common dolphins: reduced avail- ability of prey caused by overfishing and habitat degradation; contamination by xenobiotic chemicals resulting in immunosuppression and reproductive impairment; envi- ronmental changes such as increased water temperatures affecting ecosystem dynamics; and incidental mortality in fishing gear, especially gillnets. The cumulative importance of these factors is poorly understood, and as a result, few conservation measures have been implemented. 4. This paper reviews current knowledge and suggests priorities for action aimed at identi- fying and mitigating the main threats to common dolphins in the Mediterranean, with the ultimate goal of restoring the species' favourable conservation status in the region.
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mixed species associations of striped dolphins stenella coeruleoalba short beaked common dolphins Delphinus Delphis and risso s dolphins grampus griseus in the gulf of corinth greece mediterranean sea
2002Co-Authors: Alexandros Frantzis, Denise L HerzingAbstract:Surveys to assess cetacean presence were conducted in July 1995 and 1997 in the Gulf of Corinth, which is an almost-enclosed sea in Greece, Eastern Mediterranean. The dolphin sighting frequencies were high (0.043 sightings/km). Four dolphin species were encountered: striped dolphins (Stenella coeruleoalba), short-beaked common dolphins (Delphinus Delphis), Risso’s dolphins (Grampus griseus) and bottlenose dolphins (Tursiops truncatus). Bottlenose dolphins were encountered only once. Thirteen dolphin sightings were single-species (striped dolphins) and seven were mixed-species with either two species (striped and common dolphins in five sightings), or three species (striped, common, and Risso’s dolphins in two sightings) in the group. In all mixed-species sightings, Risso’s dolphins and common dolphins were always and by far the minority species present. To date, no singlespecies groups of Risso’s or short-beaked common dolphins have been observed in the Gulf of Corinth. Interspecific rake marks on the Risso’s dolphins, and behaviours observed through video analysis, indicate potentially complex and regular interspecific interactions. Our results support the idea that interspecific interactions between sympatric cetacean species in the area are common, and apparently complex.
Vincent Ridoux - One of the best experts on this subject based on the ideXlab platform.
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vaginal calculi in the eastern north atlantic common dolphins Delphinus Delphis induction mechanisms and possible effects on fecundity
Frontiers in Marine Science, 2021Co-Authors: Willy Dabin, Bastien Rochowski, Michel Daudon, Vincent RidouxAbstract:The proper management of cetacean populations requires life history and demographic parameters to be estimated at population level. In this study we focus on a reproductive pathology that has the potential to alter reproductive rate: the vaginal calculi or stones. The present work documents vaginal calculi prevalence and structure in the eastern North Atlantic common dolphin Delphinus Delphis in order to infer their likely mechanisms of induction and possible effects on fecundity. The work is based on routine examinations and necropsies of stranded marine mammals reported by the French stranding scheme from 1972-2012. Vaginal calculi were described and measured, and their composition was analysed by Fourrier-Transformed Infra-Red (FTIR) spectroscopy. Necropsies and reproductive tract examinations were performed on 435 female common dolphins since 1972 along the French coasts, of which 14 showed vaginal calculi, representing 3.2% of the examined females. All females with calculi were older than 7, and there was no relationship of calculus size with age. Histopathology revealed lesions due to an inflammatory response to the presence of the calculi: chronicle vaginitis, variable endometritis and cystitis. Calculus size varied from 1-21 cm in maximum dimension and 4-1460 g in mass. Their internal structure was homogeneous, particularly due to the absence of core material, hence corresponding to the definition of primary calculi. All calculus spectra showed almost identical compositions, with struvite (magnesium ammonium phosphate hexahydrate) representing on average 87% of calculus mass. Dysfunction of the uro-genital tract, such as vesico-vaginal fistulae, would be the likely initial pathological condition that led to the formation of these stones. Both the initial chemical condition in the vagina and the resulting formation of a calculi are obstacles to successful reproduction.
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Small cetacean species selected for this study.
'Public Library of Science (PLoS)', 2021Co-Authors: Vadim Pavlov, Vincent Ridoux, Cecile Vincent, Bjarni Mikkelsen, Justine Lebeau, Ursula SiebertAbstract:1 –Phocoena phocoena, 2 –Delphinus Delphis, 3 –Tursiops truncatus, 4 –Lagenorhynchus acutus, 5 –Lagenorhynchus albirostris, 6 –Globicephala melas, 7 –Balaenoptera acutorostrata.
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Dorsal fin and tail fluke’s outline.
'Public Library of Science (PLoS)', 2021Co-Authors: Vadim Pavlov, Vincent Ridoux, Cecile Vincent, Bjarni Mikkelsen, Justine Lebeau, Ursula SiebertAbstract:1 –Phocoena phocoena, 2 –Delphinus Delphis, 3 –Tursiops truncatus, 4 –Lagenorhynchus acutus, 5 –Lagenorhynchus albirostris, 6 –Globicephala melas, 7 –Balaenoptera acutorostrata.
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Do ovarian scars persist with age in all Cetaceans: new insight from the short-beaked common dolphin (Delphinus Delphis Linnaeus, 1758)
Marine Biology, 2008Co-Authors: Willy Dabin, François Cossais, Graham J. Pierce, Vincent RidouxAbstract:The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins ( Delphinus Delphis ) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.
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Insights on common dolphin (Delphinus Delphis) social organization from genetic analysis of a mass-stranded pod
Behavioral Ecology and Sociobiology, 2008Co-Authors: Amélia Viricel, Patricia E. Rosel, Allan E Strand, Vincent Ridoux, Pascale GarciaAbstract:Compared to terrestrial mammals, little is known of cetacean social systems as they are generally less accessible to behavioral investigations due to their aquatic environment. The present study investigates group structure of the pelagic common dolphin, Delphinus Delphis , using genetic markers. Tissue samples from 52 individuals representing a recent live mass-stranding event were compared to 42 single strandings taken from presumably different groups. The mass-stranding event occurred in 2002 on the French coast of the English Channel, whereas the single strandings were collected between 1993 and 2003 along the western coast of France (Bay of Biscay and English Channel). Analysis of mitochondrial DNA control region sequences indicated that genetic variability within the mass-stranded pod was similar to variability observed in single strandings. The mass-stranded group was composed of 41 different mitochondrial haplotypes or matrilines while the single strandings revealed 29 different haplotypes. Analysis of 11 microsatellite loci revealed that average relatedness of the mass-stranded pod was not different from average relatedness among all single strandings suggesting that individuals within the group had no closer kin relationships than animals taken from presumably different groups. These results do not support a matriarchal system and suggest that common dolphins constituting a pod are not necessarily genetically related.
Graham J. Pierce - One of the best experts on this subject based on the ideXlab platform.
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distribution and habitat modelling of common dolphins Delphinus Delphis in the eastern north atlantic
Journal of the Marine Biological Association of the United Kingdom, 2019Co-Authors: Ana M Correia, Graham J. Pierce, Agatha Gil, Raul Valente, Massimiliano Rosso, Isabel SousapintoAbstract:The eastern North Atlantic (ENA) has many highly productive areas where several species of cetaceans have been recorded, with the common dolphin (Delphinus Delphis) being one of the most frequently sighted species. However, its spatial and temporal distribution in high seas is poorly known. The study presents the results from 5 years of cetacean monitoring in the ENA (2012–2016) aboard cargo ships that follow the routes from Continental Portugal to the Macaronesian archipelagos and north-west Africa. Common dolphin was the most frequently sighted cetacean with 192 occurrences registered on effort and an overall encounter rate of 0.36 sightings/100 nmi. The species was distributed in coastal and offshore waters, but absent from the Canaries and Cape Verde islands. Statistical ‘habitat’ models were developed to describe and explain the occurrence of sightings of the species: variables affecting detection of dolphins had a small impact and there were clear spatiotemporal distribution patterns, influenced to some degree by environmental variables. Predicted probability of occurrence was highest in coastal waters of continental Portugal and around the Azores. The models, combined with maps of distribution, were useful to identify important areas for the species, which could be the focus of future conservation efforts. Common dolphin presence was related to depth, distance to coast and seamounts, seabed slope, chlorophyll concentration, sea-surface temperature and sea level anomalies; the possible ecological significance of these relationships is explored.
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assessing the environmental status of the short beaked common dolphin Delphinus Delphis in north western spanish waters using abundance trends and safe removal limits
Progress in Oceanography, 2017Co-Authors: Camilo Saavedra, Graham J. Pierce, Tim Gerrodette, Maite Louzao, J Valeiras, Salvador Garcia, Santiago Cervino, Begona M SantosAbstract:Abstract Monitoring and assessment of the status of marine mammal populations is a requirement of the European Marine Strategy Framework Directive (MSFD). Due to the difficulty of collecting data in the marine environment and because many populations of these highly mobile species inhabit waters of several Member States, monitoring of marine mammals is particularly challenging. In the present work we have used a 10-year time-series of data collected from multidisciplinary research surveys to estimate common dolphin (Delphinus Delphis) abundance and trends in continental shelf waters of the northwest Spanish sub-region. We argue that this approach provides a valuable addition to large-scale dedicated surveys, offering a shorter interval between surveys and hence offering the possibility to track abundance changes at a regional scale. Trends in the number of dolphins present in the study area over the last 10 years show a mean increase of about 9.6% per year, which results in an evaluation of Good Environmental Status for the species in the area using the abundance indicator adopted in the framework of the MSFD. Data obtained from dedicated dual-platform surveys have been used to correct the detection bias in our data collected using single-platforms (attraction toward the observation platform and animals missed on the track-line), to obtain absolute abundance estimates for calculating bycatch limits. The average abundance over the study period was 12,831 dolphins [CI 95%; 9025, 18,242] calculated with the conventional distance sampling methodology, 4747 [3307, 6816] corrected for attraction and missed animals on the track-line, and 22,510 [15,776, 32,120] corrected only for missed animals on the track-line. The estimated safe bycatch limit for this area calculated from these abundance values were 218 [153, 310], 81 [56, 115] and 383 [268, 546] per year, respectively. Comparing these figures with estimates based on different sources, the percentage of dolphins that die in this study area is higher than the maximum limit allowable under the OSPAR criteria for population mortality adopted as an indicator for the MSFD.
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Do ovarian scars persist with age in all Cetaceans: new insight from the short-beaked common dolphin (Delphinus Delphis Linnaeus, 1758)
Marine Biology, 2008Co-Authors: Willy Dabin, François Cossais, Graham J. Pierce, Vincent RidouxAbstract:The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins ( Delphinus Delphis ) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.
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long term dietary segregation of common dolphins Delphinus Delphis in the bay of biscay determined using cadmium as an ecological tracer
Marine Ecology Progress Series, 2005Co-Authors: Virginie Lahaye, Willy Dabin, Graham J. Pierce, Paco Bustamante, Jerome Spitz, Krishna Das, Florence CaurantAbstract:Dietary studies in marine mammals are traditionally performed by stomach contents analyses, which may be insufficient to determine long-term dietary preferences of these upper level predators. Our primary objective was to test the efficiency of trace metal measurements as comple- mentary tools in dietary studies. Variations in cadmium (Cd) exposure through the diet and its effec- tive renal levels in the short-beaked common dolphin Delphinus Delphis were investigated to study the long-term feeding ecology of this predator in the neritic and oceanic waters of the Bay of Biscay. Based upon previous stomach contents analyses, the main prey occurring in the diet of common dol- phins were analysed for their Cd contents. Results showed that cephalopods, and especially oceanic Cranchids and Histioteuthids, constituted a major source of Cd for common dolphins. Estimated Cd intake would therefore be 12 times higher in oceanic common dolphins (1400 ± 65 µg d -1 ) compared to neritic ones (120 ± 30 µg d -1 ). Accumulation of renal Cd concentrations with age was 5 times higher in by-caught oceanic dolphins than neritic ones (p < 0.0001). Within the neritic area, renal Cd accu- mulation rate was 2 times higher in by-caught individuals compared to stranded ones (p = 0.002). Thus, the use of Cd concentrations in by-caught dolphins proved efficient for assessing the existence of dietary segregation between neritic and oceanic common dolphins from the Bay of Biscay. However, using Cd data to make inferences about the feeding ecology of stranded animals should be considered cautiously.
Willy Dabin - One of the best experts on this subject based on the ideXlab platform.
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vaginal calculi in the eastern north atlantic common dolphins Delphinus Delphis induction mechanisms and possible effects on fecundity
Frontiers in Marine Science, 2021Co-Authors: Willy Dabin, Bastien Rochowski, Michel Daudon, Vincent RidouxAbstract:The proper management of cetacean populations requires life history and demographic parameters to be estimated at population level. In this study we focus on a reproductive pathology that has the potential to alter reproductive rate: the vaginal calculi or stones. The present work documents vaginal calculi prevalence and structure in the eastern North Atlantic common dolphin Delphinus Delphis in order to infer their likely mechanisms of induction and possible effects on fecundity. The work is based on routine examinations and necropsies of stranded marine mammals reported by the French stranding scheme from 1972-2012. Vaginal calculi were described and measured, and their composition was analysed by Fourrier-Transformed Infra-Red (FTIR) spectroscopy. Necropsies and reproductive tract examinations were performed on 435 female common dolphins since 1972 along the French coasts, of which 14 showed vaginal calculi, representing 3.2% of the examined females. All females with calculi were older than 7, and there was no relationship of calculus size with age. Histopathology revealed lesions due to an inflammatory response to the presence of the calculi: chronicle vaginitis, variable endometritis and cystitis. Calculus size varied from 1-21 cm in maximum dimension and 4-1460 g in mass. Their internal structure was homogeneous, particularly due to the absence of core material, hence corresponding to the definition of primary calculi. All calculus spectra showed almost identical compositions, with struvite (magnesium ammonium phosphate hexahydrate) representing on average 87% of calculus mass. Dysfunction of the uro-genital tract, such as vesico-vaginal fistulae, would be the likely initial pathological condition that led to the formation of these stones. Both the initial chemical condition in the vagina and the resulting formation of a calculi are obstacles to successful reproduction.
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importance of biological parameters in assessing the status of Delphinus Delphis
Marine Ecology Progress Series, 2009Co-Authors: Sinead Murphy, Rob Deaville, Emer Rogan, Willy Dabin, Alfredo Lopez, Arliss J Winship, P D Jepson, Robert J Reid, Chris Spurrier, Angel F GonzalezAbstract:Short-beaked common dolphins Delphinus Delphis in the eastern North Atlantic (ENA) are subject to mortality due to entanglement in various types of fishing gear. However, for this region, there is no population-level information available on trends in abundance, (incidental) mortality rates or even the actual distributional range. Working under the assumption that only 1 population exists in ENA waters, the current study presents basic life history data and investigates whether biological information obtained from postmortem data is, in itself, useful for managing this population. Life his- tory parameters were estimated by analysing postmortem data obtained over a 16 yr period by UK, Irish, French, Galician (northwest Spain) and Portuguese stranding and bycatch observer pro- grammes. An annual pregnancy rate of 26%, a calving interval of 3.79 yr, an average age attained at sexual maturity of 8.22 yr and an average length at sexual maturity of 188 cm were determined. With respect to the findings based solely on mortality data, significance testing failed to detect differences that could be construed as evidence of the population exhibiting what might be density-dependent compensatory responses. The low annual pregnancy rate reported throughout the sampling period may suggest either that the level of anthropogenic mortality did not cause a substantial population level decline, or a prey base declining at approximately the same rate as the dolphin population. However, this approach alone does not facilitate an assessment of the current state of the D. Delphis population in the ENA. Population abundance estimates, trends in abundance and knowledge of fac- tors that affect the dynamics of the population, such as annual mortality rates in fisheries, temporal variations in prey abundance and effects of contaminants on reproductive activity, are required not only to set management objectives, but also to give context to cross-sectional life history information.
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Do ovarian scars persist with age in all Cetaceans: new insight from the short-beaked common dolphin (Delphinus Delphis Linnaeus, 1758)
Marine Biology, 2008Co-Authors: Willy Dabin, François Cossais, Graham J. Pierce, Vincent RidouxAbstract:The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins ( Delphinus Delphis ) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.
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Trace element levels in foetus-mother pairs of short-beaked common dolphins (Delphinus Delphis) stranded along the French coasts
Environment International, 2007Co-Authors: Virginie Lahaye, Willy Dabin, Paco Bustamante, Carine Churlaud, Florence CaurantAbstract:Tissues of foetus-mother pairs of common dolphins (Delphinus Delphis) stranded along the French coasts (Bay of Biscay and English Channel) were analysed for their Cd, Cu, Hg, Se and Zn contents. In the kidneys, foetal Cd levels were extremely low, and strong relationships between Cu and Zn suggested the involvement of metallothioneins since early foetal life. The results also indicated a limited maternal transfer of Hg during pregnancy since levels in the tissues of foetuses were below 1 µg.g-1 w.wt. However, hepatic Hg levels in foetuses increased with body length, and were also proportionate to maternal hepatic, renal and muscular Hg levels. Lastly, affinities between Hg and Se in tissues would participate in Hg neutralisation in both mothers - through tiemannite granules - and foetuses - through reduced glutathione -, counteracting the toxic effects linked to the particularly high quantities of methyl-Hg to which marine mammals are naturally exposed.
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long term dietary segregation of common dolphins Delphinus Delphis in the bay of biscay determined using cadmium as an ecological tracer
Marine Ecology Progress Series, 2005Co-Authors: Virginie Lahaye, Willy Dabin, Graham J. Pierce, Paco Bustamante, Jerome Spitz, Krishna Das, Florence CaurantAbstract:Dietary studies in marine mammals are traditionally performed by stomach contents analyses, which may be insufficient to determine long-term dietary preferences of these upper level predators. Our primary objective was to test the efficiency of trace metal measurements as comple- mentary tools in dietary studies. Variations in cadmium (Cd) exposure through the diet and its effec- tive renal levels in the short-beaked common dolphin Delphinus Delphis were investigated to study the long-term feeding ecology of this predator in the neritic and oceanic waters of the Bay of Biscay. Based upon previous stomach contents analyses, the main prey occurring in the diet of common dol- phins were analysed for their Cd contents. Results showed that cephalopods, and especially oceanic Cranchids and Histioteuthids, constituted a major source of Cd for common dolphins. Estimated Cd intake would therefore be 12 times higher in oceanic common dolphins (1400 ± 65 µg d -1 ) compared to neritic ones (120 ± 30 µg d -1 ). Accumulation of renal Cd concentrations with age was 5 times higher in by-caught oceanic dolphins than neritic ones (p < 0.0001). Within the neritic area, renal Cd accu- mulation rate was 2 times higher in by-caught individuals compared to stranded ones (p = 0.002). Thus, the use of Cd concentrations in by-caught dolphins proved efficient for assessing the existence of dietary segregation between neritic and oceanic common dolphins from the Bay of Biscay. However, using Cd data to make inferences about the feeding ecology of stranded animals should be considered cautiously.
Rocio Espada - One of the best experts on this subject based on the ideXlab platform.
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injuries healing and management of common dolphins Delphinus Delphis in human impacted waters in the south iberian peninsula
Journal of the Marine Biological Association of the United Kingdom, 2020Co-Authors: Liliana Olayaponzone, Rocio Espada, Estefania Martin Moreno, Isabel Cardenas Marcial, J C GarciagomezAbstract:This study focuses on the dolphins populating the water between Gibraltar and Algeciras in the south Iberian Peninsula, an area subjected to pressure due to high human activity. The area is considered an important feeding and breeding ground for common dolphins (Delphinus Delphis). Due to the degree of residence of some specimens, and the large gap in knowledge about the evolution of wounds in D. Delphis specimens with lacerations, this work sought to perform the following analyses: identify lacerated individuals; characterize sequences of ‘before – during – after’ with respect to the occurrence of lacerations; and associate the type of injury with its severity. This work will inform future studies by expanding a database on injured individuals and contribute to periodical monitoring of specimens that frequent these geographic areas. Between 2013 and 2017, we were able to track the healing process of five injured individuals of common dolphins from a whale-watching platform thanks to photo identification. The animals exhibited fresh external wounds from different sources. In the majority of individuals, the wound-healing processes lasted 3–21 weeks. The frequency with which sightings are made and knowledge about the local population will help track injured animals, follow their wound evolution, and document their survival rates. The documented injuries inflicted by human interactions described in this paper may include fishing interactions and propeller strikes, probably as a consequence of the high intensity of recreational fishing and whale-watching activities in the area.
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hybridization in the wild between tursiops truncatus montagu 1821 and Delphinus Delphis linnaeus 1758
PLOS ONE, 2019Co-Authors: Rocio Espada, Liliana Olayaponzone, Luisa Haasova, Estefania Martin, J C GarciagomezAbstract:A case of intergeneric hybridization in the wild between a female bottlenose dolphin (Tursiops truncatus) and a short-beaked common dolphin (Delphinus Delphis), considered members of 'vulnerable' and 'endangered' subpopulations in the Mediterranean, respectively, by the International Union of Conservation of Nature is described in this paper. The birth of the hybrid was registered in the Bay of Algeciras (southern Spain) in August 2016, and the animal has been tracked on frequent trips aboard dolphin-watching platforms. This unique occurrence is the result of an apparent ongoing interaction (10 years) between a female bottlenose dolphin and common dolphins. The calf has a robust body with length similar to Tursiops, while its lateral striping and coloration are typical of Delphinus. It displays the common dolphin's 'criss-cross' pattern. However, the thoracic patch is lighter than in D. Delphis and its dorsal area is light grey, with a 'V' shape under the dorsal fin. This paper also provides a comprehensive mini-review of hybridizations of T. truncatus with other species.